import java.util.*;

class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
      this.val = val;
    }
}

public class Test {
    //字符串去重
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        scanner.close();
        HashSet<Character> hs = new HashSet<>();
        for(char ch : str.toCharArray()) {
            hs.add(ch);
        }
        for (char c:hs) {
            System.out.print(c);
        }
    }

    //按之字形顺序打印二叉树
    public ArrayList<ArrayList<Integer>> Print (TreeNode pRoot) {
        ArrayList<ArrayList<Integer>> ret = new ArrayList<>();
        if (pRoot == null) {
            return ret;
        }
        //创建一个队列
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(pRoot);
        //标记
        boolean flg = true;
        while (!queue.isEmpty()) {
            int size = queue.size();
            //创建数组
            ArrayList<Integer> tmp = new ArrayList<>();
            //弹出元素
            while (size != 0) {
                TreeNode cur = queue.poll();
                tmp.add(cur.val);
                if (cur.left != null) {
                    queue.offer(cur.left);
                }
                if (cur.right != null) {
                    queue.offer(cur.right);
                }
                size--;
            }
            if (flg) {
                flg = false;
            } else {
                Collections.reverse(tmp);
                flg = true;
            }
            ret.add(tmp);
        }
        return ret;
    }

    //判断是不是完全二叉树
    public boolean isCompleteTree(TreeNode root) {
        if(root == null) return true;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            if (cur != null) {
                queue.offer(cur.left);
                queue.offer(cur.right);
            } else {
                break;
            }
        }
        //遍历队列
        while (!queue.isEmpty()) {
            TreeNode cur = queue.peek();
            if (cur == null) {
                queue.poll();
            } else {
                return false;
            }
        }
        return true;
    }
}












